Hydrogenation Catalysts Comprising a Mixed Oxide Comprising a Promoter Metal

ABSTRACT

A process is disclosed for producing ethanol, comprising contacting hydrogen and a feed stream comprising acetic acid in a reactor in the presence of a catalyst comprising a binder and a mixed oxide comprising a promoter metal and tin, and preferably also comprising cobalt. The promoter metal is selected from the group consisting of rhenium, ruthenium, rhodium, palladium, osmium, iridium, platinum, and combinations thereof. The feed stream may comprises pure acetic acid or may comprise a mixture of 50 to 95 wt. % acetic acid and 5 to 50 wt. % ethyl acetate.

FIELD OF THE INVENTION

The present invention relates generally to processes for hydrogenatingacetic acid to form ethanol and to novel catalysts comprising a mixedoxide comprising a promoter metal, and tin and/or cobalt for use in suchprocesses and catalyst preparation thereof.

BACKGROUND OF THE INVENTION

Ethanol for industrial use is conventionally produced from petrochemicalfeed stocks, such as oil, natural gas, or coal, from feed stockintermediates, such as syngas, or from starchy materials or cellulosicmaterials, such as corn or sugar cane. Conventional methods forproducing ethanol from petrochemical feed stocks, as well as fromcellulosic materials, include the acid-catalyzed hydration of ethylene,methanol homologation, direct alcohol synthesis, and Fischer-Tropschsynthesis. Instability in petrochemical feed stock prices contributes tofluctuations in the cost of conventionally produced ethanol, making theneed for alternative sources of ethanol production all the greater whenfeed stock prices rise. Starchy materials, as well as cellulosicmaterial, are converted to ethanol by fermentation. However,fermentation is typically used for consumer production of ethanol, whichis suitable for fuels or human consumption. In addition, fermentation ofstarchy or cellulosic materials competes with food sources and placesrestraints on the amount of ethanol that can be produced.

As an alternative to fermentation, ethanol may be produced byhydrogenating acetic acid and esters thereof. Ethanol production via thereduction of acetic acid generally uses a hydrogenation catalyst. Thereduction of various carboxylic acids over metal oxides has beenproposed.

EP0175558 describes the vapor phase formation of carboxylic acidalcohols and/or esters such as ethanol and ethyl acetate from thecorresponding mono and di-functional carboxylic acid, such as aceticacid, in the presence of a copper oxide-metal oxide supported catalyst,such as CuO/ZnAl₂O₄. A disadvantage with copper oxide catalysts incarboxylic acid hydrogenation reactions is the lack of long-termcatalyst stability.

U.S. Pat. No. 4,398,039 describes a process for the vapor phasehydrogenation of carboxylic acids to yield their corresponding alcoholsin the presence of steam and a catalyst comprising the mixed oxides ofruthenium, at least one of cobalt and nickel, and optionally one ofcadmium, zinc, copper, iron, rhodium, palladium, osmium, iridium andplatinum. The total loading of active metals is 5%. A process is furtherprovided for the preparation of carboxylic acid esters from carboxylicacids in the absence of steam utilizing the above-identified catalysts.

U.S. Pat. No. 4,517,391 describes preparing ethanol by hydrogenatingacetic acid under superatmospheric pressure and at elevated temperaturesby a process wherein a predominantly cobalt-containing catalyst is usedand acetic acid and hydrogen are passed through the reactor, at from 210to 330° C., and under 10 to 350 bar, under conditions such that a liquidphase is not formed during the process. The cobalt-containing catalystcontains, as active components, from 50 to 80% by weight of Co, from 10to 30% by weight of Cu, from 0 to 10% by weight of Mn, from 0 to 5% byweight of Mo and from 0 to 5% by weight of phosphoric acid, thepercentages being based on the metal content.

U.S. Pat. No. 4,918,248 describes producing an alcohol by catalyticallyreducing an organic carboxylic acid ester with hydrogen in the presenceof a catalyst obtained by reducing a catalyst precursor comprising (A)copper oxide and (B) titanium oxide and/or titanium hydroxide at aweight ratio of (A) to (B) in the range between 15/85 and 65/35. Thecomponent (A) may alternatively be a composite metal oxide comprisingcopper oxide and up to 20 wt. % of zinc oxide.

Other hydrogenation catalysts that are not metal oxides have also beenproposed. U.S. Pat. No. 6,495,730 describes a process for hydrogenatingcarboxylic acid using a catalyst comprising activated carbon to supportactive metal species comprising ruthenium and tin. U.S. Pat. No.6,204,417 describes another process for preparing aliphatic alcohols byhydrogenating aliphatic carboxylic acids or anhydrides or esters thereofor lactones in the presence of a catalyst comprising platinum andrhenium. U.S. Pat. No. 5,149,680 describes catalytic hydrogenation ofcarboxylic acids and their anhydrides to alcohols and/or esters in thepresence of a catalyst containing a Group VIII metal, such as palladium,a metal capable of alloying with the Group VIII metal, and at least oneof the metals rhenium, tungsten or molybdenum. U.S. Pat. No. 4,777,303describes the production of alcohols by the hydrogenation of carboxylicacids in the presence of a catalyst that comprises a first componentwhich is either molybdenum or tungsten and a second component which is anoble metal of Group VIII on a high surface area graphitized carbon.U.S. Pat. No. 4,804,791 describes another production process of alcoholsby the hydrogenation of carboxylic acids in the presence of a catalystcomprising a noble metal of Group VIII and rhenium.

Thus, further improvements to hydrogenation catalysts that demonstratehigh stability, conversion of acetic acid, and other oxygenates, withhigh selectivity to ethanol are needed.

SUMMARY OF THE INVENTION

In a first embodiment of the present invention, there is provided aprocess for producing ethanol, comprising contacting acetic acid in areactor in the presence of a catalyst comprising a binder and a mixedoxide comprising a promoter metal, cobalt, and tin, wherein the promotermetal is selected from the group consisting of rhenium, ruthenium,rhodium, palladium, osmium, iridium, platinum, and combinations thereof,wherein the combined metal amount of the mixed oxide is at least 40 wt.%, based on the total weight of the catalyst. Preferably, the promotermetal is selected from the group consisting of rhenium, ruthenium, andcombinations thereof. The promoter metal may be present in an amountfrom 0.01 to 10 wt. %, based on the total weight of the catalyst. In oneembodiment, the combined metal amount of the mixed oxide is from 40 to90 wt. %, based on the total weight of the catalyst. The mixed oxide maybe present in an amount from 60 to 90 wt. %, e.g., from 70 to 85 wt. %,based on the total weight of the catalyst. The mixed oxide loading isdetermined prior to reducing any of the metals of the mixed oxide. Thetotal tin loading of the catalyst is from 10 to 60 wt. %, based on themetal content of the catalyst. The total cobalt loading of the catalystis from 10 to 60 wt. %, based on the metal content of the catalyst. Thecatalyst has a molar ratio of cobalt to tin from 2:1 to 0.75:1. In oneembodiment, the mixed oxide further comprises nickel and the totalnickel loading of the catalyst is from 2 to 40 wt. %, based on the metalcontent of the catalyst. In another embodiment, the catalyst issubstantially free of metals selected from the group consisting of zinc,zirconium, cadmium, copper, manganese, and molybdenum. The binder isselected from the group consisting of silica, aluminum oxide, andtitania. The binder loading may be from 5 to 40 wt. %, e.g., 10 to 20wt. %, based on the total weight of the catalyst.

The contacting of the catalyst comprising the mixed oxide with aceticacid may be performed in a vapor phase at a temperature of 200° C. to350° C., an absolute pressure of 101 kPa to 3000 kPa, and a hydrogen toacetic acid mole ratio of greater than 4:1. In one embodiment, thecatalyst comprising the mixed oxide may be contacted with a mixed streamcomprising from 50 to 95 wt. % acetic acid and from 5 to 50 wt. % ethylacetate.

In a second embodiment, there is provided a process for producingethanol comprising contacting hydrogen and a feed stream comprisingacetic acid in a reactor in the presence of a catalyst comprising abinder and a mixed oxide comprising a promoter metal and tin, whereinthe promoter metal is selected from the group consisting of rhenium,ruthenium, rhodium, palladium, osmium, iridium, platinum, andcombinations thereof, wherein the combined metal amount of the mixedoxide is at least 40 wt. %, based on the total weight of the catalyst.In one embodiment, the mixed oxide further comprises cobalt. The totalcobalt loading of the catalyst may be from 10 to 60 wt. %, based on themetal content of the catalyst.

In a third embodiment, there is provided a process for producing ethanolcomprising contacting hydrogen and a feed stream comprising acetic acidin a reactor in the presence of a catalyst comprising a binder, a mixedoxide comprising a promoter metal and cobalt, wherein the total cobaltloading of the catalyst is from 10 to 60 wt. %, based on the metalcontent of the catalyst, and the promoter metal is selected from thegroup consisting of rhenium, ruthenium, rhodium, palladium, osmium,iridium, platinum, and combinations thereof. The promoter metal ispresent in an amount from 0.01 to 10 wt. %, based on the total weight ofthe catalyst. The mixed oxide may also further comprise tin. The mixedstream may comprise from 50 to 95 wt. % acetic acid and from 5 to 50 wt.% ethyl acetate.

In a fourth embodiment, there is provided a process for producingethanol comprising contacting acetic acid in a reactor in the presenceof a catalyst comprising a binder and a mixed oxide comprising apromoter metal, cobalt, and tin, wherein the promoter metal is selectedfrom the group consisting of rhenium, ruthenium, rhodium, palladium,osmium, iridium, platinum, and combinations thereof, wherein thecatalyst is substantially free of metals selected from the groupconsisting of zinc, zirconium, cadmium, copper, manganese, andmolybdenum. The mixed oxide may be present in an amount from 40 to 90wt. %, e.g., from 60 to 90 wt. % or from 70 to 85 wt. %, based on thetotal weight of the catalyst.

In a fifth embodiment, there is provided a catalyst comprising a binderand a mixed oxide comprising a promoter metal, cobalt, and tin, whereinthe promoter metal is selected from the group consisting of rhenium,ruthenium, rhodium, palladium, osmium, iridium, platinum, andcombinations thereof, wherein the combined metal amount of the mixedoxide is at least 40 wt. %, based on the total weight of the catalyst.The promoter metal may be present in an amount from 0.01 to 10 wt. %,based on the total weight of the catalyst. The mixed oxide may bepresent in an amount from 60 to 90 wt. %, e.g., from 70 to 85 wt. %,based on the total weight of the catalyst.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to processes for producing ethanol byhydrogenating acetic acid in the presence of a catalyst comprising abinder and a mixed oxide comprising a promoter metal, and tin and/orcobalt. The promoter metal may enhance the catalytically activity and inaddition advantageously improve ethyl acetate conversion so that thecrude ethanol produce contains lower amounts of ethyl acetate. Inaddition, other impurity formation, e.g., diethyl ether, may be reducedby using a catalyst comprising a mixed oxide comprising a promotermetal, and tin and/or cobalt of the present invention. Low byproductformation reduces the separation requirements to obtain ethanol.

A mixed oxide refers to an oxide having cations of more than onechemical element. For purposes of the present invention, mixed oxidesinclude the reduced metals of the mixed oxide. In one embodiment, themixed oxide may comprise a promoter metal. In addition to the promotermetal, the mixed oxide may also comprise tin and/or cobalt, preferablyboth. In another embodiment of the present invention, the catalyst maycomprise a mixed oxide comprising a promoter metal, cobalt, tin, andnickel. The catalyst may also comprise a binder, such as an inertmaterial. Silica may be a preferred binder.

In one embodiment, the catalysts of the present invention have a highloading of active metals in the mixed oxide, which includes the promotermetals and tin and/or cobalt. The combined metal amount of the mixedoxide, which comprises the promoter metal and tin and/or cobalt, may beat least 40 wt. %, based on the total weight of the catalyst, e.g., atleast 45 wt. % or at least 50 wt. %. In terms of ranges, the combinedmetal amount of the mixed oxide may be from 40 to 90 wt. %, based on thetotal weight of the catalyst, e.g., from 45 to 80 wt. % or from 50 to 70wt. %. Unless otherwise stated, all ranges disclosed herein include bothendpoints and all numbers between the endpoints.

Suitable promoter metals are selected from the group consisting ofrhenium, ruthenium, rhodium, palladium, osmium, iridium, platinum, andcombinations thereof. Preferably, the promoter metal is rhenium,ruthenium, or combinations thereof. In one embodiment, the promotermetal is present in an amount from 0.01 to 10 wt. %, based on the totalweight of the catalyst. More preferably the promoter metal is present inan amount from 0.05 to 3 wt. %, based on the total weight of thecatalyst. Without being bound by theory, the promoter preferably as apotential activity on acid hydrogenation and ethyl acetate hydrolysis.

In one embodiment, the catalyst may comprise a mixed oxide comprising apromoter metal, cobalt and tin, wherein the mixed oxide is present in anamount from 60 to 90 wt. %, based on the total weight of the catalyst.This amount is determined prior to reducing any of the metals of themixed oxide. Preferably, the mixed oxide may be present in an amountfrom 70 to 85 wt. %, based on the total weight of the catalyst. Thetotal cobalt loading of the catalyst may be from 10 to 60 wt. %, e.g.,from 25 to 45 wt. % or from 30 to 40 wt. %, based on the total metalcontent of the catalyst. The total tin loading of the catalyst may befrom 10 to 60 wt. %, e.g., from 35 to 55 wt. %, based on the total metalcontent of the catalyst. Lower loadings of cobalt and tin of less than10 wt. % are to be avoided since this may decrease the conversion ofacetic acid and/or selectivity to ethanol.

In one embodiment, when cobalt and tin are both used, the mixed oxide ofthe present invention has been found to be effective with a molar ratioof cobalt to tin that is from 2:1 to 0.75:1, e.g., from 1.5:1 to 1:1 or1.4:1 to 1.1:1. A molar excess of cobalt may improve the selectivity toethanol in the catalyst. In addition, it is preferred that there is amolar excess of tin to promoter metal.

Without being bound by theory, the promoter metal, tin and/or cobalt arepredominately present on the catalyst as a mixed oxide. However, thecatalyst may contain some discrete regions of oxides of the promotermetal, cobalt oxide and tin oxide. In addition, the metallic promotermetals, cobalt or tin, i.e. as reduced metals, may also be present onthe catalyst.

In an alternative embodiment, the catalyst may comprise a promotermetal, a binder, and a mixed oxide comprising cobalt and tin, whereinthe promoter metal is in a reduced state and not part of the mixedoxide.

The mixed oxide, and thus catalyst, is preferable anhydrous.

The binder of the catalyst may be an inert material which is used toenhance the crush strength of the final catalyst. Suitable inertmaterials comprise silica, aluminum oxide, and titania. The binder maybe present in an amount from 5 to 40 wt. %, e.g. from 10 to 30 wt. % orfrom 10 to 20 wt. %, based on the total weight of the catalyst. Thus, inone embodiment, the catalyst may comprise a silica binder and a mixedoxide comprising a promoter metal, cobalt and tin.

In one embodiment, in addition to the promoter metal, the mixed oxidemay further comprise nickel. The total nickel loading of the catalystmay be from 0.5 to 40 wt. %, e.g., 1 to 20 wt. %, based on the totalmetal content of the catalyst. Without being bound by theory, nickel mayimprove the activity of the catalysts to convert acetic acid. Inaddition, nickel may be useful for converting other oxygenates in thefeed, such as ethyl acetate. The other oxygenates may also be formed inthe reactor as by-products.

In some embodiments, the mixed oxide may comprise secondary promotermetals. These secondary promoter metals may be present in minor amountsfrom 0 to 5 wt. %. The secondary promoter metals may include titanium,vanadium, chromium, manganese, iron, copper, zinc, zirconium,molybdenum, tungsten, rhenium, or cadmium. In other embodiments, themixed oxide may be substantially free of secondary promoter metals, suchas, zinc, zirconium, cadmium, copper, manganese, or molybdenum.Substantially free means that the catalyst does not contain secondarypromoter metals beyond trace amounts of less than 0.0001 wt. %. When themixed oxide is substantially free of these secondary promoter metals, itis preferred that the binder, and thus catalyst are also substantiallyfree of these secondary promoter metals.

The surface area of the catalyst comprising a mixed oxide comprisingpromoter metal, tin, and/or cobalt may be from 100 to 250 m²/g, e.g.,from 150 to 180 m²/g. Pore volumes are between 0.18 and 0.35 mL/g, withaverage pore diameters from 6 to 8 nm. The morphology of the catalystmay be pellets, extrudates, spheres, spray dried microspheres, rings,pentarings, trilobes, quadrilobes, multi-lobal shapes, or flakes. Theshape of the catalyst may be determined by hydrogen process conditionsto provide a shape that can withstand pressure drops in the reactor.

The catalyst comprising a binder and a mixed oxide of the presentinvention has an on-stream stability for at least 200 hours at constantreaction conditions. Stability refers to a catalyst that has a change ofless than 2% in conversion and less than 2% selectivity to ethanol,after initial break-in. In addition, stability refers to a catalyst thatdoes not demonstrate any increase in by-product formation whileon-stream. This greatly improves the industrial usefulness of a catalystfor continuous production. Also, this reduces the need to change thecatalyst and reduces reactor down time for continuous processes.

The catalyst comprising a mixed oxide of the present invention may bemade by the following method. Other suitable methods may also be used inconjunction with the present invention. In one embodiment, at least twosolutions containing a metal precursor are prepared. Suitable metalprecursors may include metal halides, metal halide hydrates, metalacetates, metal hydroxyls, metal oxalates, metal nitrates, metalalkoxides, metal sulfates, metal carboxylates and metal carbonates. Apromoter metal precursor may be included in one of the solutions orprepared as a separate solution.

For purposes of the present invention, there is at least one precursorcomprising a promoter metal, and at least one precursor comprisingcobalt, and/or at least one precursor comprising tin. The precursors maybe prepared in the same solution or in different solutions. In oneembodiment, a solution comprising the promoter metal precursor andcobalt precursor is prepared. Each solution may be an aqueous solutionthat comprises water. In some embodiments, when the mixed oxidecomprises a molar excess of cobalt, at least one of the solutions maycomprise an alkali hydroxide, such as sodium hydroxide. The solutionsare combined and a binder, preferably in solid form, is added theretowhile mixing. When a halide precursor is used, the mixture may befiltered and washed to remove halide anions. The mixed solution may beaged for a sufficient period of time at a temperature from 5° C. to 60°C., e.g., from 15° C. to 40° C. To obtain an anhydrous catalyst, themixture may be dried at a temperature from 50° C. to 150° C., e.g. from75° C. to 125° C., for 1 to 24 hours. Next, the material may be calcinedin air at a temperature from 300° C. to 700° C., e.g., from 400° C. to600° C., for 0.5 to 12 hours.

When additional metals, such as nickel or a secondary promoter metaldisclosed herein, are included in the catalyst, a metal precursorthereto may be added to either the cobalt precursor solution or the tinprecursor solution. In some embodiments, a separate solution may beprepared and combined once the cobalt precursor solution and tinprecursor solution are combined.

In one embodiment, the present invention comprises a method of making acatalyst comprising a binder and a mixed oxide comprising a promotermetal, cobalt and tin, the method comprising preparing a first solutioncomprising water, a cobalt precursor and a promoter metal precursor,wherein the cobalt precursor is selected from the group consisting ofcobalt halides, cobalt halide hydrates, cobalt acetates, cobalthydroxyls, cobalt oxalates, cobalt nitrates, cobalt alkoxides, cobaltsulfates, cobalt carboxylates and cobalt carbonates and the promotermetal precursor is selected from the group consisting of promoter metalhalides, promoter metal halide hydrates, promoter metal acetates,promoter metal hydroxyls, promoter metal oxalates, promoter metalnitrates, promoter metal alkoxides, promoter metal sulfates, promotermetal carboxylates and promoter metal carbonates, and preparing a secondsolution comprising water, sodium hydroxide, and a tin precursor,wherein the tin precursor is selected from the group consisting of tinhalides, tin halide hydrates, tin acetates, tin hydroxyls, tin oxidedispersion (such as ammonia, amine dispersed dispersion or hydrateddispersion), tin oxalates, tin nitrates, tin alkoxides, tin sulfates,tin carboxylates and tin carbonates. The second solution is added to thefirst solution and then silica gel is added, in solid form, to themixture with stirring. The mixture may be dried and calcined to form acatalyst comprising a binder and a mixed oxide comprising cobalt and tinof the present invention. Sodium hydroxide may be added to the secondsolution when there is a molar excess of cobalt.

The hydrogenation reaction of a carboxylic acid, acetic acid in thisexample, may be represented as follows:

HOAc+2H₂→EtOH+H₂O

It has surprisingly and unexpectedly been discovered that the catalystsof the present invention provide high conversion of acetic acid and highselectivities to ethanol, when employed in the hydrogenation ofcarboxylic acids such as acetic acid. In addition, due to the promotermetal, the catalysts of the present invention demonstrate a favorableconversion of ethyl acetate. Embodiments of the present inventionbeneficially may be used in industrial applications to produce ethanolon an economically feasible scale.

The feed stream to the hydrogenation process preferably comprises aceticacid. In some embodiments, pure acetic acid may be used as the feed. Inother embodiments, the feed stream may contain some other oxygenates,such as ethyl acetate, acetaldehyde, or diethyl acetal, or higher acids,such as propanoic acid or butanoic acid. Minor amounts of ethanol mayalso be present in the feed stream. In one embodiment, the feed streammay comprise from 50 to 95 wt. % acetic acid, and from 5 to 50 wt. %oxygenates. More preferably, the feed stream may comprise from 60 to 95wt. % acetic acid and from 5 to 40 wt. % ethyl acetate. The otheroxygenates may originate from recycle streams that are fed to thehydrogenation reactor. In other embodiments, the feed stream maycomprise from 0 to 15 wt. % water, e.g., from 0.1 to 10 wt. % water. Anexemplary feed stream, e.g., a mixed feed stream, may comprise from 50to 95 wt. % acetic acid, from 5 to 50 wt. % ethyl acetate, from 0.01 to10 wt. % acetaldehyde, from 0.01 to 10 wt. % ethanol, and from 0.01 to10 wt. % diethyl acetal.

The process of hydrogenating acetic acid to form ethanol according toone embodiment of the invention may be conducted in a variety ofconfigurations using a fixed bed reactor or a fluidized bed reactor asone of skill in the art will readily appreciate. In many embodiments ofthe present invention, an “adiabatic” reactor can be used; that is,there is little or no need for internal plumbing through the reactionzone to add or remove heat. Alternatively, a shell and tube reactorprovided with a heat transfer medium can be used. In many cases, thereaction zone may be housed in a single vessel or in a series of vesselswith heat exchangers therebetween. It is considered significant thatacetic acid reduction processes using the catalysts of the presentinvention may be carried out in adiabatic reactors as this reactorconfiguration is typically far less capital intensive than tube andshell configurations.

Typically, the catalyst is employed in a fixed bed reactor, e.g., in theshape of an elongated pipe or tube where the reactants, typically in thevapor form, are passed over or through the catalyst. Other reactors,such as fluid or ebullient bed reactors, can be employed, if desired. Insome instances, the hydrogenation catalysts may be used in conjunctionwith an inert material to regulate the pressure drop of the reactantstream through the catalyst bed and the contact time of the reactantcompounds with the catalyst particles.

The hydrogenation reaction may be carried out in either the liquid phaseor vapor phase. Preferably the reaction is carried out in the vaporphase under the following conditions. The reaction temperature may rangefrom 200° C. to 350° C., e.g., from 200° C. to 325° C., from 225° C. to300° C., or from 250° C. to 300° C. The pressure may range from 101 kPato 3000 kPa (about 1 to 30 atmospheres), e.g., from 101 kPa to 2700 kPa,or from 101 kPa to 2300 kPa. The reactants may be fed to the reactor ata gas hourly space velocities (GHSV) of greater than 500 hr⁻¹, e.g.,greater than 1000 hr⁻¹, greater than 2500 hr⁻¹ and even greater than5000 hr⁻¹. In terms of ranges the GHSV may range from 50 hr⁻¹ to 50,000hr⁻¹, e.g., from 500 hr⁻¹ to 30,000 hr⁻¹, from 1000 hr⁻¹ to 10,000 hr⁻¹,or from 1000 hr⁻¹ to 8000 hr⁻¹.

In another aspect of the process of this invention, the hydrogenation iscarried out at a pressure just sufficient to overcome the pressure dropacross the catalytic bed at the GHSV selected, although there is no barto the use of higher pressures, it being understood that considerablepressure drop through the reactor bed may be experienced at high spacevelocities, e.g., 5000 hr⁻¹ or 8000 hr⁻¹.

Although the reaction consumes two moles of hydrogen per mole of aceticacid to produce one mole of ethanol, the actual molar ratio of hydrogento acetic acid in the feed stream may vary from 100:1 to 1:100, e.g.,from 50:1 to 1:50, from 20:1 to 1:2, or from 12:1 to 1:1. Mostpreferably, the molar ratio of hydrogen to acetic acid is greater than4:1, e.g., greater than 5:1 or greater than 8:1.

Contact or residence time can also vary widely, depending upon suchvariables as amount of acetic acid, catalyst, reactor, temperature andpressure. Typical contact times range from a fraction of a second tomore than several hours when a catalyst system other than a fixed bed isused, with preferred contact times, at least for vapor phase reactions,from 0.1 to 100 seconds, e.g., from 0.3 to 80 seconds or from 0.4 to 40seconds.

The acetic acid may be vaporized at the reaction temperature, and thenthe vaporized acetic acid can be fed along with hydrogen in undilutedstate or diluted with a relatively inert carrier gas, such as nitrogen,argon, helium, carbon dioxide and the like. For reactions run in thevapor phase, the temperature should be controlled in the system suchthat it does not fall below the dew point of acetic acid.

In particular, using catalysts and processes of the present inventionmay achieve favorable conversion of acetic acid and favorableselectivity and productivity to ethanol. For purposes of the presentinvention, the term conversion refers to the amount of acetic acid inthe feed that is converted to a compound other than acetic acid.Conversion is expressed as a mole percentage based on acetic acid in thefeed.

The conversion of acetic acid (AcOH) is calculated from gaschromatography (GC) data using the following equation:

${{AcOH}\mspace{11mu} {{Conv}.(\%)}} = {100 \star \frac{{m\; {mol}\mspace{11mu} {AcOH}\mspace{14mu} \left( {{feed}\mspace{14mu} {stream}} \right)} - {m\; {mol}\mspace{11mu} {AcOH}\mspace{14mu} ({product})}}{m\; {mol}\mspace{14mu} {AcOH}\mspace{14mu} \left( {{feed}\mspace{14mu} {stream}} \right)}}$

For purposes of the present invention, the conversion may be at least70%, e.g., at least 80% or at least 90%. Although catalysts that havehigh conversions are desirable, such as at least 90%, a lower conversionmay be acceptable at high selectivity for ethanol. In addition toconverting acetic acid, the catalysts of the present invention may alsoconvert ethyl acetate at a rate sufficient to keep the ethyl acetateamounts low in the crude ethanol product. The conversion of ethylacetate may be at least 0%, meaning there is no net production of ethylacetate, or more preferably at least 5%.

To achieve a desirable catalyst performance, it is valuable to maintainthe conversion for a long period of time under reaction condition, i.e.when exposed to hydrogen and acetic acid. In one embodiment, theconversion of the catalyst is stable, i.e. does not vary by more than2%, for a period of at least 200 total hours on stream (TOS), e.g., atleast 500 TOS or at least 750 TOS.

“Selectivity” is expressed as a mole percent based on converted aceticacid, and any ethyl acetate if present. It should be understood thateach compound converted from acetic acid has an independent selectivityand that selectivity is independent from conversion. For example, if 50mole % of the converted acetic acid and ethyl acetate is converted toethanol, we refer to the ethanol selectivity as 50%. Selectivity toethanol (EtOH) is calculated from GC data using the following equation:

${{EtOH}\mspace{11mu} {{Sel}.(\%)}} = {100 \star \frac{m\; {mol}\mspace{11mu} {EtOH}\mspace{14mu} ({product})}{\left( {m\; {mol}\mspace{14mu} {Converted\_ AcOH}} \right) + {2 \star \left( {m\; {mol}\mspace{14mu} {Converted\_ EtAc}} \right)}}}$

This equation is used when ethyl acetate is present in the feed streamand there is conversion on ethyl acetate. If pure acid is used as feed,the equation can be simplified to the following equation:

${{EtOH}\mspace{11mu} {{Sel}.(\%)}} = {100 \star \frac{m\; {mol}\mspace{11mu} {EtOH}\mspace{14mu} ({product})}{{m\; {mol}\mspace{11mu} {AcOH}\mspace{14mu} \left( {{feed}\mspace{14mu} {stream}} \right)} - {m\; {mol}\mspace{11mu} {AcOH}\mspace{14mu} ({product})}}}$

For purposes of the present invention, the selectivity to ethanol of thecatalyst is at least 70%, e.g., at least 80% or at least 90%. During thestartup or catalyst aging period, there may be a net make of ethylacetate, but the selectivity to ethyl acetate may be less than 10%,e.g., less than 6%. The selectivity to acetaldehyde and/or diethylacetate may vary depending on conversion and may be from 0 to 20%, e.g.,from 0.1 to 10% or from 0.5 to 10%. At higher conversions of aceticacid, the selectivity to acetaldehyde and diethyl acetal may decrease asmore of these compounds are converted to ethanol. In addition, theselectivity to diethyl ether should be low, less than 5%, e.g. less than3% or less than 1%.

In one embodiment of the present invention, it is also desirable to havelow selectivity to undesirable products, such as methane, ethane, andcarbon dioxide. The selectivity to these undesirable products is lessthan 5%, e.g., less than 3% or less than 1.5%. Preferably, no detectableamounts of these undesirable products are formed during hydrogenation.In several embodiments of the present invention, formation of alkanes islow, usually under 2%, often under 1%, and in many cases under 0.5% ofthe acetic acid passed over the catalyst is converted to alkanes, whichhave little value other than as fuel.

Productivity refers to the grams of a specified product, e.g., ethanol,formed during the hydrogenation based on the kilogram of catalyst usedper hour. In one embodiment of the present invention, a productivity ofat least 200 grams of ethanol per kilogram catalyst per hour, e.g., atleast 400 grams of ethanol or least 600 grams of ethanol, is preferred.In terms of ranges, the productivity preferably is from 200 to 4,000grams of ethanol per kilogram catalyst per hour, e.g., from 400 to 3,500or from 600 to 3,000.

In another embodiment, the invention is to a crude ethanol productformed by processes of the present invention. The crude ethanol productproduced by the hydrogenation process of the present invention, beforeany subsequent processing, such as purification and separation,typically will comprise primarily unreacted acetic acid and ethanol. Insome exemplary embodiments, the crude ethanol product comprises ethanolin an amount from 25 to 70 wt. %, e.g., from 30 wt. % to 60 wt. %, orfrom 40 wt. % to 55 wt. %, based on the total weight of the crudeethanol product. The crude ethanol product may also be influenced by thefeed and when a mixed feed that is higher in compounds other than aceticacid is used, the crude ethanol product may contain more impurities.Regardless of the feed, the crude ethanol product typically will furthercomprise unreacted acetic acid, depending on conversion, and water asshown in Table 1. The amount of ethyl acetate, acetaldehyde, and diethylacetal may vary. The others may include alkanes, ethers, other acids andesters, other alcohols, etc. The alcohols may be n-propanol andiso-propanol. Exemplary crude ethanol compositional ranges, excludinghydrogen and other non-condensable gases, in various embodiments of theinvention are provided below in Table 1.

TABLE 1 CRUDE ETHANOL PRODUCT COMPOSITIONS Conc. Conc. Conc. Component(wt. %) (wt. %) (wt. %) Ethanol 25 to 70   30 to 65 40 to 65 Acetic Acid0 to 30 0.1 to 20 0.5 to 10  Ethyl Acetate 0 to 20 0.1 to 15  1 to 10Acetaldehyde 0 to 10 0.1 to 5  0.5 to 2  Diethyl Acetal 0 to 10 0.1 to5  0.5 to 1  Water 5 to 35  5 to 30  5 to 25 Other 0 to 10  0 to 5 0 to1

An ethanol product may be recovered from the crude ethanol productproduced by the reactor using the catalyst of the present inventionusing several different techniques, such as distillation columns,adsorption units, membranes, or molecular sieves. For example, multiplecolumns may be used to remove impurities and concentration ethanol to anindustrial grade ethanol or an anhydrous ethanol suitable for fuelapplications. Exemplary separation and recovery processes are disclosedin U.S. Pat. Nos. 8,309,773; 8,304,586; and 8,304,587; and U.S. Pub.Nos. 2012/0010438; 2012/0277490; and 2012/0277497, the entire contentsand disclosure of which are hereby incorporated by reference.

In one embodiment, the process, including separation, may comprisehydrogenating an acetic acid feed stream in a reactor in the presence ofa catalyst comprising a binder and mixed oxide comprising a promotermetal, and tin and/or cobalt to form a crude ethanol product, separatingat least a portion of the crude ethanol product in a first column into afirst distillate comprising ethanol, water and ethyl acetate, and afirst residue comprising acetic acid, separating at least a portion ofthe first distillate in a second column into a second distillatecomprising ethyl acetate and a second residue comprising ethanol andwater, wherein the second column is an extractive distillation column,feeding an extraction agent to the second column, and separating atleast a portion of the second residue in a third column into a thirddistillate comprising ethanol and a third residue comprising water.Water from the third residue may be used as the extraction agent. Also,a fourth column may be used to separate acetaldehyde from the seconddistillate.

In another embodiment, the process, including separation, may comprisinghydrogenating acetic acid and/or an ester thereof in a reactor in thepresence of a catalyst comprising a binder and mixed oxide comprising apromoter metal, and tin and/or cobalt to form a crude ethanol product,separating a portion of the crude ethanol product in a firstdistillation column to yield a first distillate comprising acetaldehydeand ethyl acetate, and a first residue comprising ethanol, acetic acid,ethyl acetate and water, separating a portion of the first residue in asecond distillation column to yield a second residue comprising aceticacid and an vapor overhead comprising ethanol, ethyl acetate and water,removing water, using a membrane or pressure swing absorption, from atleast a portion of the vapor overhead to yield an ethanol mixture streamhaving a lower water content than the at least a portion of the vaporoverhead, and separating at least a portion of the ethanol mixturestream in a third distillation column to yield a third distillatecomprising ethyl acetate and a third residue comprising ethanol and lessthan 8 wt. % water.

The raw materials used in connection with the process of this inventionmay be derived from any suitable source including natural gas,petroleum, coal, biomass and so forth. It is well known to produceacetic acid through methanol carbonylation, acetaldehyde oxidation,ethane oxidation, oxidative fermentation, and anaerobic fermentation. Aspetroleum and natural gas prices fluctuate becoming either more or lessexpensive, methods for producing acetic acid and intermediates such asmethanol and carbon monoxide from alternate carbon sources have drawnincreasing interest. In particular, when petroleum is relativelyexpensive compared to natural gas, it may become advantageous to produceacetic acid from synthesis gas (“syngas”) that is derived from anyavailable carbon source. U.S. Pat. No. 6,232,352 the disclosure of whichis incorporated herein by reference, for example, teaches a method ofretrofitting a methanol plant for the manufacture of acetic acid. Byretrofitting a methanol plant, the large capital costs associated withCO generation for a new acetic acid plant are significantly reduced orlargely eliminated. All or part of the syngas is diverted from themethanol synthesis loop and supplied to a separator unit to recover COand hydrogen, which are then used to produce acetic acid. In addition toacetic acid, the process can also be used to make hydrogen which may beutilized in connection with this invention.

U.S. Pat. No. RE 35,377, also incorporated herein by reference, providesa method for the production of methanol by conversion of carbonaceousmaterials such as oil, coal, natural gas and biomass materials. Theprocess includes hydrogasification of solid and/or liquid carbonaceousmaterials to obtain a process gas which is steam pyrolized withadditional natural gas to form synthesis gas. The syngas is converted tomethanol which may be carbonylated to acetic acid. The method likewiseproduces hydrogen which may be used in connection with this invention asnoted above. See also, U.S. Pat. No. 5,821,111, which discloses aprocess for converting waste biomass through gasification into synthesisgas as well as U.S. Pat. No. 6,685,754, the disclosures of which areincorporated herein by reference.

Alternatively, acetic acid in vapor form may be taken directly as crudeproduct from the flash vessel of a methanol carbonylation unit of theclass described in U.S. Pat. No. 6,657,078, the entirety of which isincorporated herein by reference. The crude vapor product, for example,may be fed directly to the ethanol synthesis reaction zones of thepresent invention without the need for condensing the acetic acid andlight ends or removing water, saving overall processing costs.

In one embodiment, the process may comprise a process for the formationof ethanol comprising, converting a carbon source into acetic acid, andcontacting a feed stream containing the acetic acid and hydrogen with acatalyst comprising a binder and mixed oxide comprising a promotermetal, and tin and/or cobalt of the present invention. In anotherembodiment, the process may comprise a process for the formation ofethanol comprising converting a carbon source, such as biomass, into afirst stream comprising syngas, catalytically converting at least someof the syngas into a second stream comprising methanol, separating someof the syngas into hydrogen and carbon monoxide, catalyticallyconverting at least some of the methanol with some of the carbonmonoxide into a third stream comprising acetic acid; and reducing atleast some of the acetic acid with some of the hydrogen in the presenceof a catalyst comprising a binder and mixed oxide comprising a promotermetal, and tin and/or cobalt of the present invention into a fourthstream comprising ethanol.

Ethanol, obtained from hydrogenation processes of the present invention,may be used in its own right as a fuel or subsequently converted toethylene which is an important commodity feedstock as it can beconverted to polyethylene, vinyl acetate and/or ethyl acetate or any ofa wide variety of other chemical products. Any known dehydrationcatalyst, such as zeolite catalysts or phosphotungstic acid catalysts,can be employed to dehydrate ethanol to ethylene, as described incopending U.S. Pub. Nos. 2010/0030002 and 2010/0030001 and WO2010146332,the entire contents and disclosures of which are hereby incorporated byreference.

Ethanol may also be used as a fuel, in pharmaceutical products,cleansers, sanitizers, hydrogenation transport or consumption. Ethanolmay also be used as a source material for making ethyl acetate,aldehydes, and higher alcohols, especially butanol. In addition, anyester, such as ethyl acetate, formed during the process of makingethanol according to the present invention may be further reacted withan acid catalyst to form additional ethanol as well as acetic acid,which may be recycled to the hydrogenation process.

The catalysts of the present invention may be used with one or moreother hydrogenation catalysts in a stacked bed reactor or in a multiplereactor configuration. A stacked bed reactor is particular useful whenone catalyst is suitable for high selectivity to ethanol at lowconversions. The catalyst comprising the mixed oxide of the presentinvention may be used in combination with another hydrogenation catalystto increase the acetic acid conversion and thus improve the overallyield to ethanol. In other embodiment, the catalyst comprising the mixedoxide of the present invention may be used to convert unreacted aceticacid in a recycle stream.

In one embodiment, the catalyst comprising a binder and mixed oxidecomprising a promoter metal, and tin and/or cobalt of the presentinvention may be used in the second reactor bed of a stacked bedconfiguration. The first reactor bed may comprise a differenthydrogenation catalyst. Suitable hydrogenation catalysts are describedin U.S. Pat. Nos. 7,608,744; 7,863,489; 8,080,694; 8,309,772; 8,338,650;8,350,886; 8,471,075; 8,501,652 and US Pub. Nos. 2013/0178661;2013/0178663; 2013/0178664; the entire contents and disclosure of whichare hereby incorporated by reference. In general, the differenthydrogenation catalyst in the first bed may comprise a Group VIII metaland at least one promoter metal on a supported catalyst. Suitable GroupVIII metals may include rhodium, rhenium, ruthenium, platinum,palladium, osmium, and iridium. Suitable promoter metals may includecopper, iron, cobalt, vanadium, nickel, titanium, zinc, chromium,molybdenum, tungsten, tin, lanthanum, cerium, and manganese.Combinations of Pt/Sn, Pt/Co, Pd/Sn, Pt/Co, and Pd/Co may be preferredfor the different catalyst. The metal loadings may be from 0.1 to 20 wt.%, e.g., from 0.5 to 10 wt. %, based on the total weight of thecatalyst. The support may be any suitable support such as silica,alumina, titania, silica/alumina, pyrogenic silica, silica gel, highpurity silica, zirconia, carbon (e.g., carbon black or activated carbon)zeolites and mixtures thereof. The supported catalyst may comprise amodified support that changes the acidity or basicity of the support.The support modified may be present in an amount from 0.5 to 30 wt. %,e.g., from 1 to 15 wt. %, based on the total weight of the catalyst.Acidic modifiers may include tungsten, molybdenum, vanadium, or oxidesthereof. Suitable basic modifiers may include magnesium or calcium, suchas calcium metasilicate.

The first bed may operate under similar hydrogenation conditions as themixed oxide catalyst of the present invention. The reaction temperatureof the first bed may range from 200° C. to 350° C., e.g., from 250° C.to 300° C. The pressure may range from 101 kPa to 3000 kPa, e.g., from101 kPa to 2300 kPa. The reactants may be fed to the reactor at a gashourly space velocities (GHSV) of greater than 500 hr⁻¹, e.g., greaterthan 1000 hr⁻¹. In one embodiment, fresh hydrogen may be fed to thefirst bed and the unreacted hydrogen from the first bed is passed alongto the second bed with the reaction effluent. In other embodiments, eachbed may receive a fresh hydrogen feed.

Exemplary catalysts for the first reactor bed may comprise one or morethe following catalysts. One exemplary catalyst comprises 0.1 to 3 wt. %platinum and 0.5 to 10 wt. % tin on a silica support having from 5 to 20wt. % calcium metasilicate. Another exemplary catalyst comprises 0.1 to3 wt. % platinum and 0.5 to 10 wt. % tin on a silica support having from5 to 20 wt. % calcium metasilicate and from 0.5 to 10 wt. % cobalt.Another exemplary catalyst comprises 0.1 to 3 wt. % platinum, 0.5 to 10wt. % tin, and 0.5 to 10 wt. % cobalt on a silica support having from 5to 20 wt. % tungsten. Another exemplary catalyst comprises 0.1 to 3 wt.% platinum and 0.5 to 10 wt. % tin on a silica support having from 5 to20 wt. % tungsten, and 0.5 to 10 wt. % cobalt. Another exemplarycatalyst comprises 0.1 to 3 wt. % platinum, 0.5 to 10 wt. % tin, and 0.5to 10 wt. % cobalt on a silica support having from 5 to 20 wt. %tungsten, 0.5 to 10 wt. % tin, and 0.5 to 10 wt. % cobalt.

In one embodiment, the stack bed process may comprise introducing a feedstream of acetic acid and hydrogen into a stacked bed reactor thatcomprises a first bed and a second bed to produce a crude ethanolproduct, wherein the first bed comprises a first catalyst comprisingplatinum and tin on a first support and the second bed comprises asecond catalyst comprising a binder and mixed oxide comprising apromoter metal, and tin and/or cobalt and tin of the present invention,recovering ethanol from the crude ethanol product in one or morecolumns. The acetic acid feed stream may comprise from 5 to 50 wt. %ethyl acetate and from 50 to 95 wt. % acetic acid.

Various other combinations of hydrogenation catalyst may be readilyemployed with the catalyst comprising the mixed oxide of the presentinvention. In addition, the order of the catalyst beds in the stack bedconfiguration may be arranged as needed to achieve ethanol production athigh yields.

In addition, the catalyst comprising the mixed oxide of the presentinvention may be used in a first reactor with a copper containingcatalyst in a second reactor that is suitable for converting ethylacetate to ethanol. The second reactor may comprise a second catalystthat comprises copper or an oxide thereof. In one embodiment, the secondcatalyst may further comprise zinc, aluminum, chromium, cobalt, oroxides thereof. A copper-zinc or copper-chromium catalyst may particularpreferred. Copper may be present in an amount from 35 to 70 wt. % andmore preferably 40 to 65 wt. %. Zinc or chromium may be present in anamount from 15 to 40 wt. % and more preferably 20 to 30 wt. %.

The second bed that contains a copper catalyst may operate with areaction temperature from 125° C. to 350° C., e.g., from 180° C. to 345°C., from 225° C. to 310° C., or from 290° C. to 305° C. The pressure mayrange from 101 kPa to 3000 kPa, e.g., from 700 to 8,500 kPa, e.g., from1,500 to 7,000 kPa, or from 2,000 to 6,500 kPa. The reactants may be fedto the reactor at a gas hourly space velocities (GHSV) of greater than500 hr⁻¹, e.g., greater than 1000 hr⁻¹, greater than 2500 hr⁻¹ and evengreater than 5000 hr⁻¹.

In one embodiment, the stack bed process may comprise introducing a feedstream of acetic acid and hydrogen into a stacked bed reactor thatcomprises a first bed and a second bed to produce a crude ethanolproduct, wherein the first bed comprises a first catalyst comprising abinder and mixed oxide comprising a promoter metal, and tin and/orcobalt of the present invention and the second bed comprises a secondcatalyst comprising copper-containing catalyst of the present invention,recovering ethanol from the crude ethanol product in one or morecolumns. The acetic acid feed stream may comprise from 5 to 50 wt. %ethyl acetate and from 50 to 95 wt. % acetic acid.

The invention is described in detail below with reference to numerousembodiments for purposes of exemplification and illustration only.Modifications to particular embodiments within the spirit and scope ofthe present invention, set forth in the appended claims, will be readilyapparent to those of skill in the art.

The following examples describe the procedures used for the preparationof various catalysts employed in the process of this invention.

Example 1

An aqueous solution was prepared by dissolving 27.13 g (114.04 mmol)cobalt(II) chloride hexahydrate and 0.285 g (1.24 mmol) ruthenium(III)chloride hexahydrate in about 150 mL of deionized H₂O. Separately, anaqueous solution of sodium stannate was prepared by dissolving 20.27 g(76.02 mmol) and 3.19 g (79.74 mmol) of NaOH in about 150 mL ofdeionized H₂O. The sodium stannate solution was then added to the cobaltchloride solution using a drop funnel over 10 minutes with stirring(10-12 mL/min) at room temperature. Next, 4.875 g of SiO₂ (silica gel,solid) was added to the mixture with stirring, and it was then aged withstirring for 2 hrs at room temperature. The mixture was then aged withstirring for 2 hrs at room temperature. The material was then collectedon a Buchner funnel (Watman #541 filter paper), and washed withdeionized H₂O to remove the sodium chloride. The filtrate wasperiodically tested for Cl⁻ (using Ag⁺ solution). Approximately 1 L ofdeionized H₂O was used until no more chloride could be detected. Thesolid was then transferred into a porcelain dish, and dried overnight at120° C. under circulating air. Yield: about 29.26 g of the driedcobalt-tin hydroxo precursor. In order to obtain the anhydrous catalyst,the material was calcined at 500° C. under air for 6 hrs using a heatingrate of 3 degree/min. Yield: about 24.56 g. The material contains 80 wt.% of the mixed oxide and is represented by the formula[SiO₂—Ru(0.5)Co_(1.5)SnO_(3.5)(80)]. The surface area of this catalystis 174.68 m²/g. The pore volume is 0.298 mL/g and the catalyst has anaverage pore diameter of 6.813 nm.

Example 2

An aqueous solution was prepared by dissolving 27.13 g (114.04 mmol)cobalt(H) chloride hexahydrate and 0.57 g (2.48 mmol) ruthenium(III)chloride hexahydrate in about 150 mL of deionized H₂O. Separately, anaqueous solution of sodium stannate was prepared by dissolving 20.27 g(76.02 mmol) and 3.24 g (80.98 mmol) of NaOH in about 150 mL ofdeionized H₂O. The sodium stannate solution was then added to the cobaltchloride solution using a drop funnel over 10 minutes with stirring(10-12 mL/min) at room temperature. Next, 4.875 g of SiO₂ (silica gel,solid) was added to the mixture with stirring, and it was then aged withstirring for 2 hrs at room temperature. The mixture was then aged withstirring for 2 hrs at room temperature. The material was then collectedon a Buchner funnel (Watman #541 filter paper), and washed withdeionized H₂O to remove the sodium chloride. The filtrate wasperiodically tested for Cl⁻ (using Ag⁺ solution). Approximately 1 L ofdeionized H₂O was used until no more chloride could be detected. Thesolid was then transferred into a porcelain dish, and dried overnight at120° C. under circulating air. Yield: about 29.28 g of the driedcobalt-tin hydroxo precursor. In order to obtain the anhydrous catalyst,the material was calcined at 500° C. under air for 6 hrs using a heatingrate of 3 degree/min. Yield: about 25.07 g. The material contains 80 wt.% of the mixed oxide and is represented by the formula[SiO2-Ru(1.0)Co_(1.5)SnO_(3.5)(80)]. The surface area of this catalystis 161.37 m²/g. The pore volume is 0.269 mL/g and the catalyst has anaverage pore diameter of 6.655 nm.

Example 3

The catalysts from above examples were tested under the followingconditions. The results are shown in Table 2.

A test unit had four independent tubular fixed bed reactor systems withcommon temperature control, pressure and gas and liquid feeds. Thereactors are made of ¾″ 316 SS tubing, and are 12 inches in length. Thevaporizers are made of ½″ 316 SS tubing and are 9.5″ in length. Thereactors, vaporizers, and their respective effluent transfer lines areelectrically heated. The reactor effluents are routed to chilled watercondensers and knock-out pots. Condensed liquids are collectedautomatically, and then manually drained from knock-out pots as needed.Non-condensed gases are passed through a manual back pressure regulatorand then scrubbed through water and vented to the fume hood. A volume of10 mL of catalyst (8-10 mesh) was loaded to reactor. Both inlet andoutlet of reactor are filled with Denstone® 57 (3 mm) to form the fixedbed. The following running conditions for catalyst screening were used:

TABLE 2 Running Conditions of the Catalyst Performance Test ReactionReaction Running Feed Rate H2 Flow Temperature Pressure GHSV ConditionsLiquid Feed (ml/min) (sccm) (° C.) (psig) (hr⁻¹) 1 Pure Acid 0.097 513300 300 3318 2 Pure Acid 0.138 513 300 300 3367 3 Mixed Feed 0.138 513300 300 3367

The mixed feed comprised: 69.02% acetic acid, 20.93 wt. % ethyl acetate,5.8 wt. % ethanol, 2.39 wt. % diethyl acetal, 0.57 wt. % acetaldehydeand 0.65 wt. % water. All the mixing reactants were fed into from top ofreactor. The crude ethanol product was measured as shown in Table 3. Thebalance of the compositions in Table 3 is water.

TABLE 3 Liquid Product Effluent Compositions Catalyst Running Acetal AcHHOAc Acetone EtOH EtOAc DEE Examples Conditions # (wt %) (wt %) (wt %)(wt %) (wt %) (wt %) (wt %) 1 1 0.38 1.55 0.65 0.013 60.33 5.89 0.003 20.32 1.53 0.99 0.012 54.49 10.83 0.002 3 0.37 1.67 0.76 0.011 58.8814.23 0.017 2 1 0.37 1.28 0.52 0.012 60.30 4.85 0.004 2 0.45 1.43 0.930.013 57.23 9.49 0.003 3 0.25 1.37 0.75 0.009 56.12 17.41 0.010 3 1 0.281.34 0.57 0.013 60.26 5.35 0.001 2 0.61 1.52 2.95 0.015 56.38 8.54 0.0013 0.16 1.28 1.66 0.01 49.70 23.43 0.010

Based on the crude ethanol product, the following calculation ofconversion and selectivity was made in Table 4.

TABLE 4 Catalyst Performance with Different Running Conditions RunningHOAc EtAc EtOH EtAc EtOH Catalyst Conditions Conversion ConversionSelectivity Selectivity Productivity Examples # (%) (%) (%) (%) (g/l/h)1 1 99.37 0 87.84 9.96 346.70 2 99.01 0 80.83 16.80 462.18 3 98.90 7.8798.10 0 368.42 2 1 99.48 0 90.39 7.61 345.68 2 99.07 0 83.36 14.46482.23 3 98.95 18.81 98.25 0 375.56 3 1 99.43 0 89.60 8.32 346.26 297.05 0 84.27 13.35 484.55 3 97.63 0 93.51 4.89 336.71

In addition to the high conversions, the catalysts from Examples 1 and 2demonstrated a stable performance in terms of conversion after 750 totalhours on stream (TOS) under reaction conditions. In contrast a catalystprepared similar to Example 1, but without the ruthenium promoter hadpoor performance with conversion decreasing from 99% to 95% over thefirst 750 TOS.

Example 4

5 mL of the catalyst from Example 1 was loaded to the tubular reactorfirstly, and then 5 mL of Pt(1.09)Sn(2.5)/Co(7.5)WO₃(12)/SiO₂ was loadedon the top of the bulk oxides catalyst. Both inlet and outlet of reactorare filled with Denstone® 57 (3 mm) to form the fixed bed. Use the sametest unit as example 3 and tested with blending feed under runningconditions #3. All the mixing reactants were fed into from top ofreactor. The crude ethanol product was measured as shown in Table 5 andcatalyst performance in Table 6 below. The balance of the compositionsin Table 5 is water.

TABLE 5 Liquid Product Effluent Compositions Running Acetal AcH HOAcAcetone EtOH EtOAc DEE Conditions # (wt %) (wt %) (wt %) (wt %) (wt %)(wt %) (wt %) 3 0.25 1.41 0.63 0.008 59.25 15.44 0.142

TABLE 6 Catalyst Performance with Different Running Conditions RunningHOAc EtAc EtOH EtAc EtOH Conditions Conver- Conver- Selectiv- Selectiv-Productivity # sion (%) sion (%) ity (%) ity (%) (g/l/h) 3 99.10 27.3598.17 0 417.43

While the invention has been described in detail, modifications withinthe spirit and scope of the invention will be readily apparent to thoseof skill in the art. In view of the foregoing discussion, relevantknowledge in the art and references discussed above in connection withthe Background and Detailed Description, the disclosures of which areall incorporated herein by reference. In addition, it should beunderstood that aspects of the invention and portions of variousembodiments and various features recited below and/or in the appendedclaims may be combined or interchanged either in whole or in part. Inthe foregoing descriptions of the various embodiments, those embodimentswhich refer to another embodiment may be appropriately combined withother embodiments as will be appreciated by one of skill in the art.Furthermore, those of ordinary skill in the art will appreciate that theforegoing description is by way of example only, and is not intended tolimit the invention.

We claim:
 1. A process for producing ethanol comprising contactinghydrogen and a feed stream comprising acetic acid in a reactor in thepresence of a catalyst comprising a binder and a mixed oxide comprisinga promoter metal, cobalt, and tin, wherein the promoter metal isselected from the group consisting of rhenium, ruthenium, rhodium,palladium, osmium, iridium, platinum, and combinations thereof, whereinthe combined metal amount of the mixed oxide is at least 40 wt. %, basedon the total weight of the catalyst.
 2. The process of claim 1, whereinthe combined metal amount of the mixed oxide is from 40 to 90 wt. %,based on the total weight of the catalyst.
 3. The process of claim 1,wherein the mixed oxide is present in an amount from 60 to 90 wt. %,based on the total weight of the catalyst.
 4. The process of claim 1,wherein the promoter metal is selected from the group consisting ofrhenium, ruthenium, and combinations thereof.
 5. The process of claim 1,wherein the promoter metal is present in an amount from 0.01 to 10 wt.%, based on the total weight of the catalyst.
 6. The process of claim 1,wherein the total tin loading of the catalyst is from 10 to 60 wt. %,based on the metal content of the catalyst.
 7. The process of claim 1,wherein the total cobalt loading of the catalyst is from 10 to 60 wt. %,based on the metal content of the catalyst.
 8. The process of claim 1,wherein the catalyst has a molar ratio of cobalt to tin from 2:1 to0.75:1.
 9. The process of claim 7, wherein the mixed oxide furthercomprises nickel and wherein the total nickel loading of the catalyst isfrom 2 to 40 wt. %, based on the metal content of the catalyst.
 10. Theprocess of claim 1, wherein the catalyst is substantially free of zinc,zirconium, cadmium, copper, manganese, and molybdenum.
 11. The processof claim 1, wherein the binder is selected from the group consisting ofsilica, aluminum oxide, and titania.
 12. The process of claim 1, whereinthe binder is present in an amount from 5 to 40 wt. %, based on thetotal weight of the catalyst.
 13. The process of claim 1, wherein thecontacting is performed in a vapor phase at a temperature of 200° C. to350° C., an absolute pressure of 101 kPa to 3000 kPa, and a hydrogen toacetic acid mole ratio of greater than 4:1.
 14. The process of claim 1,wherein the feed stream comprises from 50 to 95 wt. % acetic acid andfrom 5 to 50 wt. % ethyl acetate.
 15. A process for producing ethanolcomprising contacting hydrogen and a feed stream comprising acetic acidin a reactor in the presence of a catalyst comprising a binder and amixed oxide comprising a promoter metal and tin, wherein the promotermetal is selected from the group consisting of rhenium, ruthenium,rhodium, palladium, osmium, iridium, platinum, and combinations thereof,wherein the combined metal amount of the mixed oxide is at least 40 wt.%, based on the total weight of the catalyst.
 16. The process of claim15, wherein the mixed oxide further comprises cobalt.
 17. The process ofclaim 16, wherein the total cobalt loading of the catalyst is from 10 to60 wt. %, based on the metal content of the catalyst.
 18. A process forproducing ethanol comprising contacting hydrogen and a feed streamcomprising acetic acid in a reactor in the presence of a catalystcomprising a binder, a mixed oxide comprising a promoter metal andcobalt, wherein the total cobalt loading of the catalyst is from 10 to60 wt. %, based on the metal content of the catalyst, and the promotermetal is selected from the group consisting of rhenium, ruthenium,rhodium, palladium, osmium, iridium, platinum, and combinations thereof.19. The process of claim 18, wherein the mixed oxide further comprisestin.
 20. The process of claim 18, wherein the promoter metal is presentin an amount from 0.01 to 10 wt. %, based on the total weight of thecatalyst.